Internal combustion engines perform useful work by combusting a fuel and producing expanding hot gases that act directly on and thereby move parts of the engine. Typically, the steps involved in internal combustion include 1) the intake of a vaporized fuel and an oxidizer (typically air); 2) the compression of the oxidizer; 3) the ignition of the vaporized fuel and oxidizer; 4) the combustion of the fuel and the expansion of the resulting gases which act on the engine part; and 5) the exhaust of the combustion gases. A variety of types of internal combustion engines exist, including, for example, reciprocating or piston engines, rotary engines, and turbines. However, existing engines suffer from a number of drawbacks. For example, conventional engines typically include a compression step, compressing the oxidizer and, in some cases, the fuel. This compression step is energy-intensive and requires the use of considerable starting energy and of heavy components. Reciprocating or piston engines also suffer from vibration and energy losses due to the constant momentum change of the pistons as they are repeatedly accelerated, stopped, and reversed during operation of the engine. Two-stroke reciprocating engines commonly intake fluid into a chamber while that chamber is exhausting the combustion gases from the previous cycle. Thus, the intake and/or exhaust may be open during the power cycle, thereby shortening the power cycle and allowing some unburned fuel to exhaust before combustion. Four-stroke engines suffer from the disadvantage of only producing power every other cycle. Turbines also suffer from energy losses. For example, the intake process is typically open to the combustion chamber during combustion and therefore the intake must overcome the opposing pressure of combustion. Additionally, turbines typically include an open channel from intake to exhaust, and thus do not efficiently harness energy when utilizing external pressure sources.
Internal rotary combustion engines offer some advantages over other types of engines. For example, internal rotary combustion engines are typically more compact and include fewer moving parts, e.g., no valves, connecting rods, cams, and timing chains, than conventional piston engines. Rotary engines also tend to operate more smoothly since there is no reciprocating motion of the pistons. Additionally, rotary engines may have an extended power stroke rotation of the output shaft compared to piston engines. However, typical rotary engines, such as Wankel-type internal combustion rotary engines, still suffer from a number of drawbacks. For example, many conventional rotary engines leak combustion gases, which is undesirable from a fuel efficiency and environmental standpoint. Additionally, many conventional rotary engines require an energy-intensive compression step prior to ignition.